The spectral variability of HD 192639 and its implications for the star's wind structure

We report the analysis of an extensive set of spectroscopic data of the O(f ) supergiant HD 192639. A Fourier analysis of our time-series reveals a rec urrent variability with a "period" of roughly 4.8 days which is most promin ent in the absorption components of the He II X 4686 and H alpha P-Cygni pr ofiles. The same periodicity is also detected in the blue wing of several a bsorption lines (e.g. H beta). The variations of the absorption components correspond most probably to a cyclical modulation of the amount of stellar wind material along the line of sight towards the star. The 4.8-day period affects also the morphology of the double-peaked He II lambda 4686 and HQ. emission components, although these emission components display also variat ions on other (mainly longer) time scales. The most likely explanation for the 4.8-day modulation is that this cycle reflects: the stellar rotational period (or half this period). We find that the most important observational properties can be explained - at least qualitatively - by a corotating int eraction region or a tilted confined corotating wind.